I walk as fast as i can (usually between 5.2 and 6.0 km/per hour) on the steepest incline on my treadmill everyday for 20 minutes. I also walk fast every lunch time for about 10-15 minutes (most people have to run to keep up with my walk, i have long legs <img src="i/expressions/face-icon-small-happy.gif" border="0">) and in high heels as i wear them every day. I also occasionally play indoor netball once a week depending on time availability. No oxygen needed for any of this exercise(yet).